Hydrogen has been considered as new energy source replacing petroleum in various fields from the viewponts of recent energy problems.
Heretofore, an industrial process for producing hydrogen has been classified to an electrolysis of water and a thermal decomposition of a coke or petroleum.
The foremer electrolysis of water has an advantage of use of water which is easily available as a source whereas it has disadvantages that pure water should be used as water; many electrolytic apparatuses are needed; a flexibility to excess and shortage of current is not satisfactory; and a deterioration is caused by a carbonization of an electrolyte; and disadvantages from the viewpoint of a floor space and a cost of equipments are caused.
On the other hand, the latter thermal decomposition has disadvantages that an operation is usually complicated and relatively large equipments are needed to cause relatively high cost of equipments.
Recently, it has proposed to provide a process for producing hydrogen at high efficiency by electrolysis of water by contacting a cathode using platinum black as a catalyst on one surface of an ion-exchange membrane and an anode using an alloy of platinum and a reduced ruthenium oxide as a catalyst on the other surface, as an improved process for an electrolysis of water (See U.S. Pat. No. 4,039,409).
The ion-exchange membranes used in the above process have been mainly fluorinated cation-exchange membranes having sulfonic acid group as a cation exchange group. Thus, in the conventional process, the fluorinated cation-exchange membrane having sulfonic acid group itself has been used to electrolyze water, because of the characteristics of the membrane, whereby strong acidity is given in the membrane and near the membrane.
This process overcomes certain disadvantages caused by the conventional electrolysis of water and results high efficiency at low voltage. As described above, the membrane and the electrolyte near the membrane impart strong acidic condition whereby it is necessary to use expensive acid resistant substances such as noble metal for equipments for the electrolysis especially both cathode and anode and a cost for the production of hydrogen is disadvantageously high.
The invention of U.S. Pat. No. 4,039,409 has the feature of the use of the improved electrodes made of noble metal having high acid resistance.